Off‐season spawning and factors influencing toxicity test development with topsmelt Atherinops Affinis

Abstract

AbstractThree separate groups of adult topsmelt (Atherinops a/finis) were spawned in rotation in laboratory culture over a two‐year period to provide larvae for toxicity tests. Size and viability of embryos and larvae produced during the normal summer spawning period (May‐August) were compared to those produced during the off season (October‐April). Mean embryo viability was relatively high throughout the study (82%), whereas size of larvae varied. Larval size was significantly larger during the summer spawning period than in winter. A 7‐d growth and survival toxicity test protocol was developed for topsmelt larvae. Variability of the protocol was assessed over a 12‐month period using copper chloride as a reference toxicant. Precision of 12 toxicity tests using copper was high; the intralaboratory C.V. for copper LC50s was 19%. The 7‐d larval protocol also gave comparable results in two interlaboratory toxicity tests using copper and complex effluent. This study demonstrates that topsmelt may be spawned throughout the year to provide larvae for toxicity tests and that topsmelt larvae have comparable sensitivity to other larval fishes commonly used in toxicity testing.